Last week, doctors injected embryonic stem cells into a human patient with an acute spinal cord injury. The procedure took place at Shepherd Center, a hospital and research center for spinal cord and brain injury in Atlanta, GA. The patient was the first to receive human stem cells derived from an embryo in an FDA-approved research protocol in the U.S.

The phase I trial, sponsored by Geron Corporation of Menlo Park, CA, is primarily intended to evaluate the treatment’s safety. The company has developed a way to culture and purify oligodendrocyte progenitor cells (OPCs – primitive neuronal cells) from human embryonic stem cells (h-ESCs). These precursor cells, obtained from human embryonic tissue, can be coaxed, at least in vitro, to develop into one of various mature cell types, including neurons).

So what defines stem cells?

Stem cells are considered pluripotent, meaning that they have the capacity to differentiate, or mature, into specialized, distinct cell forms depending on nearby cells and stimulatory molecules in their environment. Mature cells, by contrast, have already “decided” what kind of tissue they’ll grow into – whether that’s part of the eye, or the heart, liver tissue, nervous system or any other body component.

The idea behind stem cell therapy for spinal cord injury is to provide the wounded spine with fresh, primitive cells that might grow into neurons and replace those that have been damaged. The protocol is highly-experimental.